I am new to watching the NBA. I saw the name World Peace as #15 for the Lakers. However, I saw highlights of the same player, number, and team with the name Artest. Why these names? What is the history behind these names?
Ron Artest changed his name to Metta World Peace in 2011.
He legally changed his name from to Metta World Peace in September 2011 (Wikipedia).
After the 2013-14 NBA season, he played in China for a few months. When he first moved there, he announced that he would rename himself "The Panda's Friend" (CBS Sports). However, his name on his Chinese jersey remained Metta World Peace (or more precisely 慈世平, which is a three word/character abbreviation of his full Chinese name 慈善·世界和平).
In March 2015 he moved to play in Italy. In this YouTube video of some his highlights while in Italy, I see that the name on his Italian jersey is "The Panda's Friend". However the commentators seem to call him "Metta World Peace".
So, I do not know what his legal name actually is now.